How do I validate an octal number?
It can only contain digits 0-7, optionally prefixed by 0o/0O, with spaces or underscores as separators. If an 8 or 9 appears the calculator will raise an error.
Octal to decimal converter
Convert octal to decimal with BigInt and see the positional method (8^n) with running totals. Includes binary and hexadecimal outputs and steps.
Octal to decimal calculator online (with steps)
Convert octal numbers to decimal instantly. We validate digits 0-7, clean 0o/0O prefixes and show decimal, binary and hexadecimal outputs with clear base-8 steps.
Decimal
0
Normalized octal
0
Binary equivalent
0
Hexadecimal equivalent
0
Step-by-step
How the decimal is calculated
We multiply each octal digit by powers of 8 according to its position (right to left) and add up the products.
Frequently asked questions
How do you convert octal to decimal manually?
Write the octal value, assign powers of 8 starting at 80 on the rightmost digit and move left. Multiply each digit by its power of 8 and add the results.
Can I also get binary and hexadecimal?
Yes. Each octal digit maps to three bits so we show binary automatically. We also compute the hexadecimal equivalent to verify the decimal output.
